The prior art is already aware of hydraulic systems in powered and working vehicles, such as tractors with power steering and powered back-hoe implements. In these prior systems, it is common to have one hydraulic system, including a hydraulic pump, for operating the powered steering mechanism and to have another hydraulic system, including another hydraulic pump, for operating the powered implement, such as the back-hoe mounted on the vehicle. An example of the latter mentioned arrangement of a hydraulic system for a powered implement is shown in U.S. Pat. No. 3,047,171, and that disclosure is incorporated in this description.
Therefore, in the prior art, two hydraulic pumps are required, each one providing the hydraulic pressure for the respective hydraulic system mentioned, such as the power steering system and the working implement system.
The present invention improves upon the prior art systems in that it provides an integrated hydraulic system wherein the vehicle power steering mechanism and the working implement mechanism, and their respective hydraulic controls, are integrated into one system. In accomplishing this objective, the system of this invention requires only one hydraulic pump for powering both the power steering and the working implement.
Another object and advantage of the present invention is to provide a hydraulic system wherein there is an improved steering response in the powered steering mechanism at low vehicle engine speeds, and there is also conservation of power and energy through eliminating the power steering hydraulic pump and also eliminating its usual attached and associated elements which result in energy losses, compared to the system described herein.
In accomplishing the aforementioned objectives, the hydraulic system of the present invention utilizes an open-center steering valve with power beyond capability and an open-center loader-backhoe valve wherein the hydraulic elements are integrated into one system for the dual functions referred to herein. In this arrangement, the hydraulic pressure in the power steering portion of the system can be limited to a lower pressure than that in the loader-backhoe portion of the system, and thus the respective portions receive their required pressures but not excessive pressures. Further, this system recognizes that it is common practice that when the power steering portion of the system is being used the loader-backhoe portion of the system does not necessarily require a high pressure; and, conversely, when the loader-backhoe portion of the system is being used, the power steering portion of the system need not operate and there can be complete relief of pressure in that portion of the system at that time.
Other objects and advantages will become apparent upon reading the following description in light of the accompanying drawings.